This invention relates to railway frogs.
It is well known that railway frogs are subject to extreme wear as a result of the weight of passing trains and the impact of the wheels on various parts of the frog. For example the point of frog, the area of the guards, and the heel and toe end transitions are subjected to significant impact and damage, with the point suffering notably more wear damage than the other parts. The cost of repair and replacement of the frogs is significant.
Various attempts have been made to make frogs more resistant to the stresses they undergo and to simplify their replacement.
One approach has been to provide a cast frog insert that is made of a high solidity material such as a manganese alloy. Due to the high cost of such alloys, various designs of cast inserts have in turn been developed in an attempt to minimize the size of the casting required while still retaining the structural integrity of the frog and the ability to secure it, typically by bolts, in place between the running rails.
Another approach has been to provide a welded boltless manganese frog that eliminates rail joints in order to minimize transition wear and hence to minimize the need to replace the frog.
It is also known to provide a form of welded boltless manganese frog that has a truncated heel end and a welded non-manganese heel extension to further minimize the amount of manganese alloy required in the frog but still provide the ability to weld the frog to running rails in the field.
All of such prior art relies on a unitary toe to heel structure that, while shaped and tailored to minimize its length, and to minimize rail joints and improve the ease of replacement, nonetheless must be completely replaced when worn. The present invention seeks to further minimize the cost and difficulty of repairing a frog insert and to obviate the need to replace the entire casting.
This and other objects of the invention will be better understood by reference to the detailed description of the preferred embodiment which follows.
In considering approaches to solving the problems presented by the prior art, the inventors first conceived of providing a removable point that would be seated on a protrusion rising from the flangeways of the casting. However, it was found that the secure retention of the removable point on the casting presented a problem. Combined with the impact stresses to which the removable point was subjected, the result was plastic deformation of the element and difficulty in effectively replacing it. The solution of the present invention elegantly resolves this difficulty.
A frog insert assembly according to one aspect of the invention comprises a casting defining the heel and toe sections of a frog. The portion of the casting intermediate the heel and toe sections consists of an integral spine extending between the heel and toe sections. An intermediate point section, the base of which is hollowed out, is removably seated on the spine. The top surface of the intermediate section defines the point, a small portion to the toe side of the point, a small portion to the heel side of the point, and the flangeways in the vicinity of the point.
The frog assembly is mounted on a base plate, for example by means of clips or hold-downs. In the preferred embodiment, the clips or hold-downs are used on the heel and toe sections of the casting, as well as on the removable intermediate section, while the spine itself is not directly restrained.
In order to accommodate an intermediate section that can define the flangeways, the spine is preferably of a height that is less than the height of the flangeways in relation to the base plate. Preferably the difference between the heights is at least 3.5 cm.
The heel and toe ends of the intermediate section as well as the mating portions of the heel and toe sections of the casting that face the intermediate section are preferably mitred to ensure proper and snug positioning of the intermediate piece and to minimize wear at the transition.
In another embodiment of the invention, the heel and toe sections of the frog are cast separately along with a separate spine and a separate removable intermediate piece.
In one aspect, the invention comprises a railway frog insert assembly comprising a casting defining the heel and toe sections of a frog and having an integral spine extending between said heel and toe sections, and an intermediate section removably seatable over the spine between the heel and toe sections.
In another aspect of the invention, the intermediate section also comprises a top surface defining a point and a flangeway adjacent each side of the point.
In yet another aspect, the top surface further defines portions of a frog, said portions including a portion of the frog to the toe side of the point, a portion of the frog to the heel side of the point, and at least a portion of a flangeway on the toe side of the point.
In another aspect, the frog insert assembly comprises a casting defining the heel and toe sections of a frog and having an integral spine extending between the heel and toe sections, and an intermediate section removably seatable over the spine between the heel and toe sections. The intermediate section includes a base with a hollowed out channel, and the intermediate section is removably seatable over the spine by seating the channel over the spine.
In another aspect, the previously referenced top surface defines at least a point and a flangeway adjacent each side of the point. In a further aspect, it also defines a portion of the frog to the toe side of the point, a portion of the frog to the heel side of the point, and at least a portion of a flangeway on the toe side of the point.
In another aspect of the invention, the intermediate section includes a top surface, a base having two sides and a lateral extension extending from each of said sides of the base.
In yet a further aspect, the invention comprises a frog assembly comprising a base plate, the frog insert assembly as described above and a plurality of retainers engaging each of said heel section, said toe section and said extensions to the base plate. Preferably the spine is not retained in engagement to the base plate.
In yet another aspect, the invention comprises a frog insert assembly according to any of the aspects described above, wherein the heel and toe ends of the intermediate section have mitred cuts, and the facing heel and toe sections of the assembly have corresponding mitred cuts.
The foregoing was intended as a broad summary only and of only some of the aspects of the invention. It was not intended to define the limits or requirements of the invention. Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiment and to the claims.